Duplex fabric paper press



Oct. 26, 1965 D. B. WICKER ETAL 3,

DUPLEX FABRIC PAPER PRESS Filed Jan. 24, 1965 2 Sheets-Sheet 1 FIG. I

2 RYER FROM To D WEB FORMER 2 32 5 W0 A rxrx rxrx/wxn /6 f Q/ U a a 42 4 34/ 44 2 FIG. 4

i I J 3 40 4440 36 I 42 34 wmt tl 38 x FIG. 5

United States Patent 3,214,330 DUILEX FABRIC PAPER PRESS Dan B. Wicker, Loudonville, and Irving H. Peters, Slingerlands, N.Y., assignors to Huyck Corporation, Eatamford, Conn, a corporation of New York Filed Ian. 24, 1963, Ser. No. 253,557 6 Claims. (Cl. I62358) This invention relates to fabric presses of papermaking machines and more particularly to improved felts, fabrics and rollers for use in combination with fabric presses.

This invention relates more specifically to the step in which water is removed from moist, freshly formed paper sheets by running them between rotating cylindrical squeeze rolls commonly known as presses. It is the traditional practice to convey such running sheets into and through press nips by means of running endless bands comprising woven and felted textile fibers, and traditionally known as papermakers felts. The earliest presses used solid cylindrical rolls, and the expressed water necessarily drained through the felt and flowed countercurrently over the surface of the rotating lower roll until removed from the system by falling free therefrom. A later embodiment constituted the so-called suction press in which the roller that runs inside the felt comprises a hollow cylinder with perforations therethrough; a suction box with vacuum is utilized inside the hollow cylinder to apply vacuum to the felt and paper sheet at and adjacent the nip region. The openings in the perforated roll provide void space into which the expressed water moves momentarily while passing beyond the nip region. Under usual circumstances, most of the water is thereafter flung out of the roll by centrifugal force and is caught by a guard pan and removed from the system. Some of the water, of course, may be drawn by the vacuum within the suction box and removed through the vacuum pump.

In an improved apparatus known as a fabric press, plain rollers are used, the sheet being passed therebetween in combination with a conventional felt. In one embodiment there runs inside the felt a mat or fabric with voids therein to provide the space to receive the expressed water while it passes through and beyond the nip region. Such apparatus anticipates the water remaining in the voids of the fabric and being removed in an other part of the path of travel by the action of centrifugal force. Another embodiment of the fabric press provides for the expressed water largely to pass through the voids of the fabric and be deposited as a film on the surface of the cooperating roller. A wiper or scraper thereafter removes the film from the roller such that a substantially water-free surface moves into the ingoing side of the nip.

It is evident that in both modifications of the fabric press the major consideration is provision of the necessary void space for expressed water to occupy while passing through and beyond the nip region. If such space is not provided, the squeezing action results in a backup and accumulation of excess water at the ingoing side of the nip in such a manner as to dilute the sheet and cause a disturbance or destruction of its formation in an action commonly spoken of as crushing. In the embodiment of the fabric press that anticipates the expressed water largely remaining in the fabric that runs inside the felt, it is desirable to enhance the forces that retain water within this structure. In the embodiment that provides for the water to pass through the fabric and onto the surface of the cooperating roll, it is desirable for the fabric to retain a minimum amount of water and for a maximum amount to be transmitted to the roll surface. In all embodiments of the fabric press the provision of void volume is a 3,214,330 Patented Oct. 26, 1965 major consideration and, hence, the felt preferably should provide the void space but minimize the possible transmission of water in such space back into the sheet after passing through the emerging side of the nip. In all embodiments, it is desirable that the felt be capable of receiving water from the sheet as pressure is imposed thereon, but also be capable of easily releasing it to the fabric and through the fabric to the roller surface that runs therein. The inside fabrics or mats mentioned all are relatively incompressible in order that the void volume be preserved throughout the high pressure region of the nip. None of the fabrics or mats now in use provide a barrier to impede transfer of water through the structure and onto the surface of the inside roll. Therefore, the embodiments disclosed have the disadvantage of the structure of the foraminate band striking through the felt to emboss and imprint on the paper sheet that is pressed therewith to produce a condition commonly spoken of as marking. Furthermore, in the embodiment of the fabric press that presupposes the retention of the expressed water within the voids of the inside fabric (rather than their transfer to the surface of the inside roll) there is a disadvantage of uninhibited transfer of water entirely through the fabric to a point on the surface of the roll that does not conform to the concept of the disclosure.

Accordingly, it is an object of this invention to provide improved apparatus and a method for removing water from a wet paper web.

It is another object of this invention to provide apparatus having combinations of press felts and fabrics which will retain increased amounts of water which may be pressed from wet paper webs, and will transport the water through the nip region of press rolls to selected dewatering regions.

A further object of this invention is to provide a combination of press felts and fabrics which will minimize the extent of re-wetting of a pressed paper web and which will permit press rolls to be operated at higher press loads without crushing the paper web.

Still another object of this invention is to provide apparatus having combinations of press felts and fabrics which will facilitate transference of expressed water to an inner press roll.

Yet another object of this invention is to provide a press roll with a readily wetted surface in order to facilitate the transference of expressed water out of the voids of the felt and the fabric and onto the press roll surface in the form of a film.

Other objects will be apparent to those skilled in the art from reading the following description taken in conjunction with the accompanying drawings, in which:

FIGURE 1 is a diagrammatic view of a press section of a papermaking machine;

FIGURE 2 is a schematic cross-sectional view of the wet paper Web and supporting felts as passed between the press rolls taken along line 2-2 of FIG. 1;

FIGURE 3 is a schematic plan view, on an enlarged basis, of an embodiment of a duplex press felt useful in this invention;

FIGURE 4 is a cross-sectional view of the duplex press felt along line 4-4 of FIG. 3;

FIGURE 5 is another cross-sectional view of the duplex press felt along line 5-5 of FIG. 3;

FIGURE 6 is an enlarged, schematic plan view of another duplex press felt useful in this invention;

FIGURE 7 is a cross-sectional view of the duplex press felt of FIG. 6 taken along line 7-7;

FIGURE 8 is another cross-sectional view of the duplex press felt of FIG. 6 taken along line 88;

FIGURE 9 is an enlarged, schematic plan view of another duplex press felt useful in this invention;

FIGURE is a cross-sectional view of the duplex press felt of FIG. 9 taken along line 1010;

FIGURE 11 is another cross-sectional view of the duplex press felt of FIG. 9 taken along line 11-11; and

FIGURE 12 is an enlarged schematic cross-sectional view of another duplex press felt useful in this invention.

The objects of this invention are accomplished by the use of a fabric press in which a duplex felt is used in conjunction with a flexible water receiving mat to carry a wet paper web between press rolls where water is forced from the Web into the duplex felt and the mat which then transport the water to regions where the water is removed. The water receiving mat may be made of rubber, plastic or similar solid material and desirably is formed with holes, cavities or pores sufficiently large to prevent Water received therein from being held by capillarity against the centrifugal forces encountered in pressing operations carried out at usual papermaking speeds. Alternatively, the mat may be Woven from relatively nonabsorbent material or may constitute flexible wire netting or a simplex felt, the interstices thereof constituting the holes, cavities or pores.

The duplex, or two-layered, press felt has a first felted layer of low void volume and a second layer of high void volume, which is significantly less felted than the first layer or is not felted. The low void volume layer may be soft or flexible, and the high void volume layer may be hard or stiff. It is preferred that the low void volume layer be highly compressible and the high void volume layer be less compressible, the degree of compressibility of the latter being suflicient to avoid marking the wet paper web.

The preferred materials for the low void volume layer are predominantly natural animal fibers, such as wool. The high void volume layer desirably contains a significant amount of synthetic polymer yarns, such as polyamides, polyesters, and the like. Desirably the synthetic yarns constitute from about to 100% of the high void volume layer although lesser ratios may be used.

It has been found that unexpectedly improved water removal is obtained from using a duplex felt in combination with a water receiving mat, arranged with the water receiving mat running inside the duplex felt to transport a wet paper web between the press rolls. Without wishing to be bound by a theory of operation, it is believed that because of the high void volume and low compressibility of the high void volume layer of the press felt, higher press loads may be applied without water buildup before the nip and without crushing. Also the low void volume, felted layer of the duplex felt hinders water from being transmitted back into the pressed paper web.

It is a feature of this invention that there is little tendency for the water to return from the high void volume layer into the low void volume layer, and so back into the paper, after the pressure of the press roll is removed. Moreover, the void sizes in the low void volume layer are sufficiently small that retained water will not be expelled from the layer by the centrifugal forces encountered in pressing operations at speeds usually employed in papermaking, as happens with more loosely woven or loosely felted fabrics. Most of the Water is retained in the high void volume layer of the felt and in the water receiving mat and is removed at points beyond the press rolls by well known means, such as described below.

As shown in FIGURES l and 2, the moist paper web 2 from a Web forming section (not shown) of a papermaking machine is carried by water receiving mat 4 and duplex felt 6 between press roll 8 and inner press roll 10. Water receiving mat 4 runs inside duplex felt 6. Face layer 5 (FIG. 2) of duplex felt 6 runs in contact with wet paper web 2; rear layer 7 runs in contact with water receiving mat 4. Paper web 2, after pressing, continues into the drying section (not shown). Part of the ex pressed Water passes through water receiving mat 4 and duplex felt 6 and is transferred to the surface of inner press roll it) from which it is removed by wiper, or doctor blade 11.

Part of the retained water is removed as water receiving mat 4 and duplex felt 6 pass compressed air supply conduits 12, 14 respectively. The water is blown into receiving trays 16, 18 from which it drains. Water is also removed as water receiving mat 4 and duplex felt 6 pass over suction boxes 20, 22 and is drawn into the suction boxes from which it drains.

A preferred embodiment of the duplex felt 6 used in: this invention is shown in FIGURES 3, 4 and 5. Duplex felt is made up of low void volume layer 32 (FIG. 4) and high void volume layer 34 which are woven together into a unitary fabric by yarns 36. Fine layer 32 is made up of yarns 38 and 40, which comprise a 4-harness satin, or crow-foot, weave in a relatively fine, low void volume structure. The yarns 38 and 40 are soft, low twisted construction, are easily felted and provide good cushion. In this embodiment layer 32 is preferentially disposed on the face or paper-sheet-contacting side of press felt 6.

Layer 34 is made up of yarns 42 and 44 which comprise a plain Weave in a relatively coarse, high void volume structure. Yarns 42, 44 are less compressible than yarns 38, 4t and if made predominantly of wool are hard twisted and difiicult to felt.

Yarns 36 stitch the two layers 32, 34 together. If yarns 36 were absent, layers 32 and 34 would come out of the loom as two entirely separate pieces. With the yarns 36 joining them, layers 32 and 34 have the character of one fabric with a fine, well felted structure with low void volume for layer 32, and a coarse, less felted high void volume structure for layer 34.

An alternate embodiment of a duplex felt useful in this invention is the 4-harness satin shown in FIGURES 6, 7 and 8. In this embodiment the press felt S0 is formed of yarns 52, 54. The yarns 52 have a soft twist, are well felted and compressible to provide cushion. Yarns 54 have a hard twist, are less felted and are less compressible than yarns 52. Yarns 52 are disposed predominantly adjacent to face side 51 of duplex face and so contact Wet paper web 2. Due to the predominant layering of yarns 52, 54 felt 50 has a fine, Well felted, low void volume layer on face side 51 and a coarse layer with a high void volume on rear side 53.

Another embodiment of a duplex felt useful in this invention is shown in FIGURES 9, l0 and 11. Felt is desirably comprised of yarns in two distinct-woven patterns. Yarns 62, 64 desirably comprise a 4-harness satin, or crow-foot, weave in a relatively fine, low void volume structure. Yarns 62 are desirably of soft, low twisted construction, are well felted and provide cushion. Yarns 62 are preferentially disposed at face side 66 of felt 60. Yarns 64 are desirably less felted and less compressible. Yarns 64 are preferentially disposed at rear side 68 of felt 60.

Yarns 70, 72 desirably comprise a plain Weave in a coarse, high void volume structure. Yarns 70 are similar to yarns 62 and preferentially are disposed predominantly on face side 66 of the 4-harness weave. Yarns 72 are similar to yarns 64 and preferentially are disposed predominantly on rear side 68 of the 4-harness satin weave. Yarns 74 comprise locking stitches inserted at regular intervals in order more firmly to interlock the two woven elements of felt 60. Without yarns 74 the two woven elements would be loosely interlocked; with the locking stitches therein, the final felt 60 has the character of one fabric with a fine, well-felted, low void volume structure disposed preferentially at face side 66 and a coarse, less felted, high void Volume structure preferentially disposed at rear side 68.

Other weaves are operable in the practice of this invention, such as a S-harness or 6-harness satin, or the like, for the low void volume layer, and a basket weave, twill, broken twill, or the like for the high void volume layer.

In general, any two layered fabric is operable as the duplex felt in the practice of this invention which has one layer of a fine, well felted, compressible, low void volume structure and a second layer of a coarse, high void volume, less felted, less compressible structure.

Another embodiment of this invention is shown in FIGURE 12. Duplex felt 80 desirably comprises a scrim or base fabric 82, woven in the manner described above or woven with other weaves such as a plain weave, a twill weave, a 4-harness satin, or the like. A non-woven batt 84 formed by carding machines or garnetts may be applied to scrim 82 by the use of barbed needles which so entangle the batt with the woven structure that there is a high degree of adhesion between the two layers. In such a combination, the batt side, or face side 86 of the felt desirably is provided with a denser structure and lower void volume than the scrim, or rear side 88. Moreover, batt side 86 may be made denser than textile structures that are made by weaving alone. The water removal effect of the needled batt structure will desirably be at least as great and, in most instances, greater than woven structures.

Although the duplex felts useful in this invention are operable in their natural state, their effectiveness may be enhanced by treating them to make them water attractive or water repellent. For instance, by treating the felt to render it water repellent the tendency of Water to return from the mat layer into the felt is reduced. Thus, the re-Wetting of the paper Web as it emerges from the press rolls is reduced. The repellent nature of the felt will not prevent water from being forced from the wet paper web through it by the mechanical pressure applied by the press roll. Where it is desired that as much water as possible be retained in the felt or mat, their treatment to render them water receptive will increase their water retention capability.

The surface of inner press roll may be treated to render it water receptive and so aid in the transference of expressed water to it.

When operating a fabric press on the principle of transmitting the expressed Water to the surface of the roller running within the fabric, it is preferred to have the fabric water repellent in order to enhance such transmission.

There are various methods of rendering textile structures, including fibers, yarns and fabrics water repellent. One method comprises the application of fiuorocarbons, such as Minnesota Mining & Manufacturing Corporations compound FC208. This compound has the chemical formula C F and is a modified acrylate. It is available as a non-ionic emulsion of the fluorocarbon resin containing 28% solvent. An impregnating solution may be prepared by dissolving 0.1 part of sodium chloride or sodium acetate in 100 parts by weight of a bath. The fluorocarbon resin emulsion equal to 3.5 parts by weight of the bath is added with sufficient agitation to distribute the resin. A solution is prepared containing one part of fluorocarbon solids which is sufiicient to fairly Wet a fabric. Isobutanol may be added to the solution in the amount of 4% of the bath volume as a fugitive wetting agent if the fabrics do not wet out readily. The remainder of the bath is water. After the material has been thoroughly wetted, the bath solution is drained, and the material is brought to a wet pick-up of about 100% of its dry weight. The treated material is then dried and cured at 250-300 F. for five to ten minutes to provide a dry weight pick-up of about 1%. Thereafter, the resultant fabric is water repellent, has a noticeably decreased tendency to absorb water and has an increased tendency to release or shed water.

Another method of treating textile materials to make them water repellent is to apply an organo-polysiloxane containing a zirconium or tin salt. Such a material is available under the name Cravenette SWS with catalyst 54. The latter material is an emulsion consisting of 30% by weight of silicone solids and employing a metallic organic salt as a catalyst. The materials to be treated are immersed in a bath and extraneous material removed. The repellent in the amount of 5% by weight of dry material is diluted with its own volume of water and distributed throughout the bath by agitation. The catalyst in the amount of 2% by weight of the dry material is similarly diluted and added to the bath. The pH of the bath varies between about 2.5 and. 7. The material is retained in the bath for 30 minutes or until the milky appearance caused by the repellent disappears and is then removed and dried. No thermal cure is required because the resin cures at room temperature. A dry weight pickup of about 1% is obtained and will produce the water repellent properties desired.

Another type of water repellent treatment for textile materials comprises the application of stearamido-methylpyridinium chloride. A representative bath is prepared by dispersing at l30-140 F. an amount of the compounds equivalent to 6% of the weight of the bath, using an amount of solvent equivalent to 30% of the final bath volume. The bath is continuously stirred and diluted to the desired volume with water. Sodium acetate in the amount of 10% of the weight of the compound added is dissolved separately in water and added to the bath. The final bath temperature should be about F. A sufficient amount of liquid is added to cause a Wet Weight pick-up of 60% of the dry weight of the material. After the material is dried it is cured at 300 F. for two minutes to provide a final dry weight pick-up of about 4%. The resultant fabric will thereafter show wate repellent properties.

Other methods of treating textile materials to render them water repellent involve the application of such material as Atcodri Z which is a mixture of a zirconium salt and a paraffin wax. The zirconium salt may be Zirconium stearate.

Still another method of making textile materials water repellent is to apply thermo-setting resins, such as Phobotex FTC along with a catalyst.

A method for treating textile materials or roll surfaces to render them more water receptive comprises the application of an anionic exchange resin containing polyoxyethyl chains and ionic groups. Such a material is available under the name Aston 108 from Onyx Oil & Chemical Company. It is applied to the material or roll surface in the form of soluble polymers containing reactive groups together with soluble multi-functional cross-linking agents. The reaction is carried out at elevated temperatures.up to about 212 F. A solution containing 25% of Aston 108, a cross-linking agent in the ratio of 7:3 to the Aston 108, and about 0.5% of an aromatic polyglycol ether, such as Neutronyx 600 is applied. to the textile or surface. Thereafter the material or surface is dried and cured with infra-red radiation at as high a temperature as it will withstand without damage thereto, but in any event at 212 F. or higher.

The terms and expressions which have been employed are used as terms of description and not of limitation, and there is no intention in the use of such terms and expressions of excluding any equivalents of the features shown and described or portions thereof, but it is recognized that various modifications are possible within the scope of the invention claimed. For instance, while the invention has been described for use with wet paper webs in papermaking processes, it is applicable as well to other absorbent materials in related processes.

What is claimed is:

11. A fabric press for removing increased amounts of water from a wet web of paper and other absorbent materials in papermaking and related processes comprising a pair of cooperating press rolls and means to transport the wet web between said press rolls, said means comprising a water receiving mat and a duplex press felt, said duplex press felt running between said mat and said wet web, said duplex felt being formed of a Well felted, compressible, relatively low void volume first layer and a less felted, less compressible, relatively high void volume second layer the void volumes of said layers being high and low relative to each other, said first layer being in contact with said wet web and said second layer being in contact with said water receiving mat.

2. A fabric press for removing increased amounts of water from a wet web of paper and other absorbent materials in papermaking and related processes comprising a pair of cooperating press rolls, and means to transport the wet web between said press rolls, said means comprising a water receiving mat and a duplex felt, said duplex felt being treated to improve its water repellency, said duplex felt running between said mat and said wet web, said duplex felt being formed of a felted first layer which has low void volume and is compressible and a second layer having high void volume and being less felted and less compressible than said first layer.

3. A fabric press for removing increased amounts of water from a wet web of paper and other absorbent materials in papermaking and related processes comprising a pair of cooperating press rolls, and means to transport the wet web between said press rolls, said means comprising a water receiving mat and a duplex felt, said water receiving mat being treated to improve its water repellency, said duplex felt running between said mat and said wet web, said duplex felt being formed of a felted first layer which has low void volume and is compressible and a second layer having high void volume and being less felted and less compressible than said first layer.

4. A fabric press for removing increased amounts of water from a wet Web of paper and other absorbent materials in paper making and related processes comprising a pair of cooperating press rolls, and means to transport the Wet web between said press rolls, said means comprising a water receiving mat and a duplex felt, said duplex felt being treated to render it water receptive, said duplex felt running between said mat and said wet web, said duplex felt being formed of a felted first layer which has low void volume and is compressible and a second lay-er having high void volume and being less felted and less conipressi-ble than said first layer.

5. A fabric press for removing increased amounts of water from a wet Web of paper and other absorbent materials in papermaking and related processes comprising a pair of cooperating press rolls, and means to transport the wet web between said press rolls, said means comprising a water receiving mat and a duplex felt, said water receiving mat being treated to render it water receptive, said duplex felt running between said mat and said wet web, said duplex felt being formed of a felted first layer which has low void volume and is compressible and a second layer having high void volume and being less felted and less compressible than said first layer.

6. A fabric press for removing increased amounts of water from a wet web of paper and other absorbent materials in papermaking and related processes comprising a pair of cooperating press rolls, and means to transport the wet web between said press rolls, said means comprising a water receiving mat and a duplex felt, the press roll adjacent said mat being treated to render it water receptive, said duplex felt running between said mat and said wet web, said duplex felt being formed of a felted first layer which has low void volume and is compressible and a second layer having high void volume and being less felted and less compressible than said first layer.

References Cited by the Examiner UNITED STATES PATENTS 1,651,476 12/27 Sheehan 139383 3,093,535 6/63 Brauns et a1. 162358 FOREIGN PATENTS 624,831 8/61 Canada. 1,198,432 6/59 France.

DONALL H. SYLVESTER, Primary Examiner. MORRIS f). WOLK, Examiner. 

1. A FABRIC PRESS FOR REMOVING INCREASED AMOUNTS OF WATER FROM A WET WEB OF PAPER AND OTHER ABSORBENT MATERIALS IN PAPERMAKING AND RELATED PROCESSES COMPRISING A PAIR OF COOPERATING PRESS ROLLS AND MEANS TO TRANSPORT THE WET WEB BETWEEN SAID PRESS ROLLS, SAID MEANS COMPRISING A WATER RECEIVING MAT AND DUPLEX PRESS FELT, SAID DUPLEX PRESS FELT RUNNING BETWEEN SAID MAT AND SAID WET WEB, SAID DUPLEX FELT BEING FORMED OF A WELL FELTED, COMPRESSIBLE, RELATIVELY LOW VOID VOLUME FIRST LAYER AND A LESS FELTED, LESS COMPRESSIBLE, RELATIVELY HIGH VOID VOLUME SECOND LAYER THE VOID VOLUMES OF SAID LAYERS BEING HIGH AND LOW RELATIVE TO EACH OTHER, SAID FIRST LAYER BEING IN CONTACT WITH SAID WET WEB AND SAID SECOND LAYER BEING IN CONTACT WITH SAID WATER RECEIVING MAT. 